UDC 62-987:666.233
M. V. Novikov, O. I. Borymsky, O. O. Leshchuk, S. B. Polotnyak, O. P. Antonyuk (Kyiv)
Modeling of the thermomechanical state of the elements of a high-pressure apparatus for the synthesis of diamonds with a developed specific surface
A study was conducted to improve the design of a high-pressure apparatus of the “anvil with recesses” type for the synthesis of diamond powders with a developed specific surface. Using the finite element method, the stress-strain state of the apparatus during its assembly and creation of high pressure, the temperature field in the apparatus and the diamond crystallization zone in the reaction volume were calculated. The improvement of the apparatus design was aimed at creating optimal temperature gradient distributions in the reaction cell, eliminating cases of pressing out of the fastening rings of the apparatus during its operation.
UDC 666.792.34:539.89
G. WITH. Oleynyk, A. AND. Shulzhenko, D. AND. Stratychuk, V. G. Gargin, V. M. Vereshchaka (Kiev)
Features of the microstructure of the composite with increased fracture toughness obtained in the B—C—Si system at high pressure
The results of the certification of the structural state of the high-density composite obtained at p = 7.7 GPa and T = 1100 °C by the method of impregnation of porous pressing of boron carbide (initial particle size — 0.5-8.0 μm) with molten silicon are presented. It was established that the main element of the microstructure of the composite are boron carbide grains with dimensions of 0.5-3.0 μm; each grain is in the shell of a solid solution of B4C—Si; the shell contains nanodisperse (20-50 nm) boron carbide-based separations, the groups of which contribute to the dispersion of the shell into fragments 0.2-0.5 microns in size. It is concluded that the increased fracture toughness of the composite can be explained mainly by a combination of two factors — the presence of a fine-grained matrix (based on shells of a solid B4C—SiC solution) with low-strength interfaces containing nanodisperse precipitates, and stress thermal and elastic anisotropy in coarse-grained component.
UDC 544.344.012:539.89
IN. WITH. Turkevich, O. G. Kulyk, A. G. Haran, I.A. Petrusha, A. N. Lutsenko, A. N. Vashchenko (Kiev)
Diagram of the state of the Al—C system at a pressure of 8 GPa
Using the methods of metallographic, X-ray, and micro-X-ray spectral analysis, phase equilibria in the double system Al—C at a pressure of 8 GPa were studied on samples obtained by quenching. Experimental results were used to find unknown parameters in phenomenological models of phases competing at high pressures. A thermodynamic calculation was performed and a diagram of the state of the Al—C system at a pressure of 8 GPa was constructed. It was found that at a pressure of 8 GPa, the incongruent nature of Al4C3 carbide melting is preserved, and in the temperature range from 2470 to 2800 K, a two-phase region Zh+A appears on the diagram.
UDC 536.42:539.89
IN. L. Solozhenko (Kyiv) A. AND. Kurakevych (Paris)
On the phase transformations of the turbostratic phases of the B—C—N system at high pressures and room temperature
Using the methods of Rietveld analysis and multiple modeling of layered B—C—N clusters with various types of lattice defects, results were obtained that make it possible to explain the experimentally observed evolution of the diffraction spectra of turbostrate graphite-like BC2N under pressure at room temperature. It is shown that at a pressure above 20 GPa, a reversible non-diffusion transformation of the initial turbostrat phase into a high-pressure phase formed by densely packed corrugated layers with a diamond-like structure occurs.
UDC 666.3:539.5
I.P. Fesenko, S. M. Dub (Kyiv)
Mechanical properties of AlN in polycrystal
Dense polycrystalline AlN samples of different structural states were obtained by hot pressing, free sintering and high-temperature annealing. The hardness and elastic modulus of AlN grains were determined using the nanoindentation method, and the plasticity parameter was calculated. The obtained values allowed us to place aluminum nitride between titanium nitride and silicon nitride in terms of increasing plasticity parameter. Aluminum nitride at an indenter movement speed of 10 nm/s is more plastic than titanium nitride, titanium carbide, titanium diboride and silicon carbide.
UDC 621.921.34:666.233:548.211
S.N. Shevchuk, V.N. Kvasnytsa, S.A. Ivakhnenko, I.S. Belousov, O.A. Zanevsky, M.A. Serga (Kyiv)
Hexaoctahedra on single crystals of synthetic diamond
Studies of the morphology of diamond single crystals obtained by the temperature gradient method when the growing temperature regime is changed. With the help of microscopic and goniometric studies, the complex cut of crystals was studied, a number of simple forms rare for diamond were established – hexaoctahedron {931}, {971}, etc., and the surface of their faces was studied. It is shown that the appearance of simple shapes on diamond crystals is associated with a large heat dissipation from the crystallization front by the growing crystal.
UDC 38.945:539.893
T. AND. Prykhna, V. B. Sverdun, V. THERE ARE. Moshchyl, N. IN. Sergiyenko, A. AND. Kordyuk, R. IN. Vyznychenko, A.V. Vlasenko, S. N. Dub, L. I. Alexandrova, A. Yu. Blacksmith (Kyiv) V. Gavalek, A. B. Surzhenko, M. Wendt (Jena, Germany) L. S. Uspenskaya (Chernogolovka, Moscow Region)
Formation of a superconducting connection between blocks of fused textured ceramics based on yttrium
The results of a study of the process of formation of superconducting connections between blocks of fused textured ceramics based on YBa2Cu3O7-d using the powdered compound TmBaCu3O7-d as an auxiliary material (solder) are presented. The optimum properties — the critical current density through the superconducting compound and material equal to 34 kA/cm2 in zero magnetic field at 77 K, the bending strength of 28-32 MPa, the microhardness of the weld and material under a Vickers indenter load of 1.96 N, respectively, 4.57±0.82 GPa and 4.82±0.45 GPa — were obtained as a result of rapid heating to a temperature of 1010 °C and cooling (excluding the texturing step during melting). Model experiments using rings of superconducting material and studying the superconducting characteristics (depending on the pinning force) using various methods allow us to conclude that the results obtained are reliable.
UDC 621.923
V. V. Skryabin, V. I. Sidorko, Yu. D. Filatov (Kyiv)
The nature of wear of the working layer of the tool during finishing of flat surfaces of products made of aluminosilicate materials
The article presents the results of a study of the nature of wear of the working layer of the tool during finishing of flat surfaces of products made of aluminosilicate materials. As a result of the analysis of kinematic schemes of stone processing, it is shown that the most uniform wear of the working layer of the tool is achieved with a scheme that is implemented on a bridge grinding and polishing machine equipped with a ferrace. For this processing scheme, the design parameters of the working layer of the tool are determined, which ensure its uniform wear.
UDC 621.922.029: 661.65
V. S. Ptashnikov (St. Petersburg)
Physical and normative hardness of abrasive tools made of highly hard and superhard materials. Part 1. Physical Hardness of Abrasive Tools
By moving from a qualitative assessment of the wear mechanism of abrasive tools during cutting to a quantitative one-parameter one using the dispersion parameter of active grains and from a standard one-parameter assessment of the relative consumption of material to its structuring, the linear-elastic nature of wear and tear of CBN tools is proven, on the basis of which the law of wear with elastic deformation of the supporting system of the binder is established, which has relevant theoretical and applied significance. Based on the law of elastic wear, the concept of physical hardness of abrasive tools is scientifically substantiated for the first time – a scientific definition of the concept of physical hardness is formulated, the criterion for its assessment and the hardness indicator are determined, ensuring compliance with the inversion principle during measurement.
UDC 621.921
V. I. Lavrinenko, V. T. Fedorenko (Kyiv)
Technological and energy aspects of accounting for and ensuring structural orientation in the working layer of grinding wheels made of STM
The article considers technological (increasing the durability of the edge of a diamond wheel under the condition of its operation simultaneously with the periphery and end, when the greatest load falls on the edge of the wheel, which leads to its greatest wear) and energy (conditions for sintering the working layer of the wheel, under which it is possible to implement a change in the structure of such a layer) aspects of the need to account for and ensure structural orientation in the working layer of a grinding wheel made of superhard materials.